Effects of nidus microarchitecture on cerebral arteriovenous malformation hemodynamics

New approaches for brain arteriovenous malformations-related epilepsy

BACKGROUND

The purpose of this review is to present the current literature and to highlight the most recent findings in brain arteriovenous malformations (bAVM)-related epilepsy research.

METHODS

We searched Medline, PubMed, Biblioinserm, Cochrane Central to study the latest research reports about the different factors that could be responsible for the genesis of bAVM-related epilepsy. We analyzed if epileptogenesis has any characteristics traits and its relation with the vascular malformation. The results of different treatments on epilepsy were considered. Typical errors that may lead towards incorrect or worse management of the seizures for these patients were also examined.

RESULTS

The development of bAVM results from multifactorial etiologies and bAVM-related epileptogenesis is likely specific for this pathology. Different types of evidence demonstrate a bidirectional relationship between bAVM and epilepsy. Currently, there is not enough published data to determine what may be the right management for these patients.

CONCLUSIONS

A better understanding of epileptogenesis in conjunction with knowledge of the complex alterations of structures and functions following bAVM-related seizures is necessary. Identification of biomarkers that can identify subgroups most likely to benefit from a specific intervention are needed to help guide clinical management. A new concept for the treatment of epilepsy related to an unruptured bAVM that cannot be treated invasively is proposed as well as new therapeutic perspectives. The next necessary step will be to propose additional algorithms to improve the development of future trials.

Microsurgical Treatment of Deep and Eloquent AVMs

Over the past 30 years, the treatment of deep and eloquent arteriovenous malformations (AVMs) has moved away from microneurosurgical resection and towards medical management and the so-called minimally invasive techniques, such as endovascular embolization and radiosurgery. The Spetzler-Martin grading system (and subsequent modifications) has done much to aid in risk stratification for surgical intervention; however, the system does not predict the risk of hemorrhage nor risk from other interventions. In more recent years, the ARUBA trial has suggested that unruptured AVMs should be medically managed. In our experience, although these eloquent regions of the brain should be discussed with patients in assessing the risks and benefits of intervention, we believe each AVM should be assessed based on the characteristics of the patient and the angio-architecture of the AVM, in particular venous hypertension, which may guide us to treat even high-grade AVMs when we believe we can (and need to) to benefit the patient. Advances in imaging and intraoperative adjuncts have helped us in decision making, preoperative planning, and ensuring good outcomes for our patients. Here, we present several cases to illustrate our primary points that treating low-grade AVMs can be more difficult than treating high-grade ones, mismanagement of deep and eloquent AVMs at the behest of dogma can harm patients, and the treatment of any AVM should be tailored to the individual patient and that patient's lesion.

Systematic Review of Functional Mapping and Cortical Reorganization in the Setting of Arteriovenous Malformations, Redefining Anatomical Eloquence

Objective: The goal of this study was to systematically review functional mapping and reorganization that takes place in the setting of arteriovenous malformations (AVMs) and its potential impact on grading and surgical decision making.

Methods: A systematic literature review was performed using the PubMed database for studies published between 1986 and 2019. Studies assessing brain mapping and functional reorganization in AVMs were included.

Results: Of the total 84 articles identified in the original literature search, 12 studies were ultimately selected. This includes studies evaluating the impact of cortical reorganization on patient outcomes and factors impacting and triggering cortical reorganization in AVM.

Conclusion: These studies demonstrate the utility of preoperative brain mapping and acknowledgment of functional reorganization in the setting of AVMs. While these findings led to alterations in Spetzler–Martin grading and subsequent surgical decision making, it remains unclear the clinical utility of this information when assessing patient outcomes. While promising, more research is required before recommendations can be made regarding functional brain mapping and cortical reorganization with respect to AVM surgery involving eloquent brain tissue.

Contrast Time-Density Time on Digital Subtraction Angiography Correlates With Cerebral Arteriovenous Malformation Flow Measured by Quantitative Magnetic Resonance Angiography, Angioarchitecture, and Hemorrhage

BACKGROUND

Digital subtraction angiography (DSA) currently provides angioarchitectural features of cerebral arteriovenous malformations (AVMs) but its role in the hemodynamic evaluation of AVMs is poorly understood.

OBJECTIVE

To assess contrast time-density time (TT) on DSA relative to AVM flow measured using quantitative magnetic resonance angiography (QMRA).

METHODS

Patients seen at our institution between 2007 and 2014 with a supratentorial AVM and DSA and QMRA obtained prior to any treatment were retrospectively reviewed. Regions of interest were selected on the draining veins at the point closest to the nidus. TT on DSA was defined as time needed for contrast to change image intensity from 10% to 100%, 100% to 10%, and 25% to 25%. TT was correlated to AVM total flow, angioarchitectural features, and hemorrhage.

RESULTS

Twenty-eight patients (mean age 35.6 yr) were included. Six patients presented with hemorrhage. Mean AVM volume was 11.42 mL (range 0.3-57.7 mL). Higher total AVM flow significantly correlated with shorter TT100%-10% and TT25%-25% (P = .02, .02, respectively). Presence of venous stenosis correlated significantly with shorter TT100%-10% (P = .04) and TT25%-25% (P = .04). AVMs with a single draining vein exhibited longer TT25%-25% compared to those with multiple draining veins (P = .04). Ruptured AVMs had significantly shorter TT10%-100% compared to unruptured AVMs (P = .05).

CONCLUSION

TT on DSA correlates with cerebral AVM flow measured using QMRA and with AVM angioarchitecture and hemorrhagic presentation. Thus, TT may be used to indirectly estimate AVM flow during angiography in real-time and may also be an indicator of important AVM characteristics associated with outflow resistance and increased rupture risk, such as venous stenosis.

In-room assessment of intravascular velocity from time-resolved rotational angiography in patients with arteriovenous malformation: a pilot study

Background

Time-resolved rotational angiography (t-RA) enables interventionists to better comprehend complex arteriovenous malformations (AVMs), thereby facilitating endovascular treatment. However, its use in evaluating hemodynamic changes has rarely been explored.

Objective

This study uses t-RA to estimate intravascular flow in patients with AVM to compare this with flow in the normal population.

Methods

Patients with available t-RA scans were prospectively categorized into one of three groups: hemorrhagic AVM, non-hemorrhagic AVM and control. Pulsatile time–density curves (TDCs) for C1, C6 and VOIMCA were used for amplitude and velocity estimation. C1 was at the cervical internal carotid artery (ICA), 2–3 cm below the carotid canal, C6 was at the paraclinoid segment of the ICA, and VOIMCA was at the junction of the first and second segment of the middle cerebral artery (MCA). A waveform amplitude ratio was defined as (peak − trough)/trough contrast intensity. VICA was defined as the distance between C6 and C1 divided by the time required for the wave to pass, and correspondingly, the average velocity of MCA (VMCA) was defined as the distance between C6 and VOIMCA divided by the duration for the same peak to travel from C6 and VOIMCA, AVM volume was estimated by MR angiography.

Results

Amplitude ratios AC1 and AC6, and average flow velocities VICA and VMCA were significantly larger in the non-hemorrhagic group than in the control group, while the hemorrhagic AVM group was not significantly different from the controls. VICA and VMCA showed moderate to good correlations with AVM volume (r=0.51 and 0.73, respectively). VMCA (33.0±9.1) was significantly lower than VICA (41.3±13.2) in the control group, but not in the two AVM groups.

Conclusion

TDC waveform propagation derived from t-RA can quantify hemodynamic differences between AVM and the control group. t-RA provides both real-time anatomic and hemodynamic evaluation, and can thus potentially improve the interventional workflow.

Validation of cerebral arteriovenous malformation hemodynamics assessed by DSA using quantitative magnetic resonance angiography: preliminary study

BACKGROUND

The hemodynamic evaluation of cerebral arteriovenous malformations (AVMs) using DSA has not been validated against true flow measurements.

OBJECTIVE

To validate AVM hemodynamics assessed by DSA using quantitative magnetic resonance angiography (QMRA).

MATERIALS AND METHODS

Patients seen at our institution between 2007 and 2016 with a supratentorial AVM and DSA and QMRA obtained before any treatment were retrospectively reviewed. DSA assessment of AVM flow comprised AVM arterial-to-venous time (A-Vt) and iFlow transit time. A-Vt was defined as the difference between peak contrast intensity in the cavernous internal carotid artery and peak contrast intensity in the draining vein. iFlow transit times were determined using syngo iFlow software. A-Vt and iFlow transit times were correlated with total AVM flow measured using QMRA and AVM angioarchitectural and clinical features.

RESULTS

33 patients (mean age 33 years) were included. Nine patients presented with hemorrhage. Mean AVM volume was 9.8 mL (range 0.3-57.7 mL). Both A-Vt (r=-0.47, p=0.01) and iFlow (r=-0.44, p=0.01) correlated significantly with total AVM flow. iFlow transit time was significantly shorter in patients who presented with seizure but A-Vt and iFlow did not vary with other AVM angioarchitectural features such as venous stenosis or hemorrhagic presentation.

CONCLUSIONS

A-Vt and iFlow transit times on DSA correlate with cerebral AVM flow measured using QMRA. Thus, these parameters may be used to indirectly estimate AVM flow before and after embolization during angiography in real time.